Electrical primer

ABSTRACT

An electrical primer having a pole piece, a plated element having an ignition bridge, a casing member and an ignitable charge arranged within an electrically conductive housing such that the ignitable charge is in operative relation with the ignition bridge and an electrically conductive connection is provided between the pole piece and the housing via the plated element and the casing member. The pole piece is accessible from the outside of the housing and is provided with a recess in the side portion facing the ignitable charge and the plated element is arranged within the recess such that the bottom surface thereof rests on the bottom of the recess of the pole piece. The plated element may also have a peripheral surface portion resting against the wall portion of the recess.

United States Patent Gawlick et al.

[ 1 Feb. 25, 1975 ELECTRICAL PRIMER [75] Inventors: Heinz Gawlick, Furth; Hellmut Bendler, Nurnberg; Uwe Brede, Schwaig, all of Germany [73] Assignee: Dynamit Nobel Aktiengesellschaft,

Troisdorf, Germany [22] Filed: Sept. 12, 1973 [21] Appl. No.: 396,438

[30] Foreign Application Priority Data Sept. l5, 1972 Germany 2245308 [52] US. Cl. 102/28 R, 102/46 [51] Int. Cl. F42b 19/12 [58] Field of Search 102/28, 46

[56] References Cited UNITED STATES PATENTS 3,018,732 H1962 Tognola lO2/46 X 3,295,446 l/l967 Harnau l02/28 3,308,758 3/1967 Stadler et a] 102/28 3,682,096 8/l972 Ludke et al l02/28 Primary ExaminerVerlin R. Pendegrass Attorney, Agent, or Firm-Craig & Antonelli [57] ABSTRACT An electrical primer having a pole piece, a plated element having an ignition bridge, a. casing member and an ignitable charge arranged within an electrically conductive housing such that the ignitable charge is in operative relation with the ignition bridge and an electrically conductive connection is provided between the pole piece and the housing via the plated element and the casing member. The pole piece is accessible from the outside of the housing and is provided with a recess in the side portion facing the ignitable charge and the plated element is arranged within the recess such that the bottom surface thereof rests on the bottom of the recess of the pole piece. The plated element may also have a peripheral surface portion resting against the wall portion of the recess.

20 Claims, 4 Drawing Figures PATENIED FEB2 51975 FIG.3

FIG.4

1 ELECTRICAL PRIMER The present invention relates to an electrical primer with an electrically conductive housing and a pole piece disposed therein and accessible from the outside, which pole piece is electrically conductively connected to the housing via a coated or plated laminated element having an ignition bridge and via an inner casing, as well as with at least one ignitable charge which is in operative connection with the ignition bridge.

DOS No. 2,020,016 discloses an electrical, metalcoated or plated primer having a mechanically solid in sulating body of, for example, glass or ceramic. A plated primer is also disclosed in US. Pat. No. 3,682,096. By vaporization, printing and/or by a chemical method, there are applied to this support an ignition bridge, e.g., of tantalum, tantalum nitride, or chromium, and the electrodes of the ignition bridge which are enlarged to provide sufficiently wide contact areas of, for example, nickel, palladium, palladium gold, platinum gold, etc. This plated element, as contrasted to the conventional electrical gap primers, has, on the one hand, an exactly defined electric resistance, so that the flawless ignition at a predetermined ignition voltage is ensured. On the other hand, since this device has no parts soldered or welded thereon, it is very shockproof, as contrasted to the conventional incandescent wire primers, so that it has proven itself very well, for example, in automatic firearms having a high firing speed and consequently high shock stresses during the introduction of the ammunition into the cartridge chamber.

However, it was found in practice, when installing this plated element into the primer housing and subsequently introducing the at least one ignitable composition by means of pressure, that the relatively brittle insulating body can be damaged under unfavorable conditions, due to the tolerances of the individual parts with respect to one another, unavoidable in mass production, at the very high pressures of application of up to about 1,500 kp/cm whereby the flawless functioning of the primer is at least made questionable. It is possible, for example, that the pole piece is not disposed exactly coaxially in the housing, but rather is seated therein in a slightly canted position. However, in such a case, the plated element placed on the pole piece is likewise disposed in such a canted position, so that, during the application of the ignitable charge or charges by means of pressure, the plated element is pressed unilaterally against the housing and is thereby damaged in certain cases.

It is therefore an object of the present invention to overcome the disadvantages of the prior art while further increasing the shockproofness of the primer utilizing the conventional plated element.

In accordance with the present invention, there is provided an electrical primer having an electrically conductive housing and a pole piece disposed therein and accessible from the outside. The pole piece is electrically conductively connected with the housing via a plated element having ignition bridge and an inner casing or sleeve. At least one ignitable charge or composition is in operative connection with the ignition bridge, by providing that the pole piece, on its side facing the at least one ignitable charge, has a cup-shaped recess wherein the plated element is arranged and rests with its bottom and peripheral surfaces against the pole piece. By means of this protected, defined arrangement ofthe plated element within the pole piece, it is advantageously ensured that the element is uniformly stressed during the assembly of the primer, as well as, for example, when feeding the ammunition into the firearm and during firing, and thus locally limited overstrains which can be the cause of functional impairment under unfavorable circumstances, are avoided.

According to a feature of the present invention, in case of very high requirements as to shockproofness and thus also very high required pressures during the pressure introduction of the at least one ignitable charge, the depth of the recess, considering an optionally provided electrical insulation between the pole piece and the inner casing, is preferably dimensioned so that the plated element is reliably supported along its entire height. The recess in the pole piece, in case of mass production, can also be manufactured very accurately in shape and dimensions simply by producing the pole piece with recess by a stamping or like procedure.

The safety attainable in this way with respect to flawless manufacture and required shockproofness is increased when the plated element more evenly contacts the bottom of the recess in the pole piece with its entire bottom surface. Therefore, in an advantageous embodiment of this invention, the provision is made that the plated element rests on the pole piece with its peripheral surface by way of a tubular extension of an insulating ring. This affords the possibility of selecting the cross section of the recess to be larger than that of the plated element, so that the bottom-side support of the latter is not impaired by the fact that the transition from the bottom of the recess to the wall thereof, rather than being sharply angular, is made to be slightly rounded, which is simpler from the viewpoint of manufacturing technique. The insulating ring, made of a synthetic resin, for example, also simultaneously prevents the direct electric contact between the pole piece and the inner casing.

in order to facilitate, on the one hand, the insertion of the plated element together with the tubular extension of the insulating ring surrounding the element into the recess of the pole piece, and, on the other hand, yet to obtain a maximally firm seating of the plated ele ment in the recess, the present invention furthermore provides the feature'of fashioning the inner wall of the recess and the outer wall of the extension in the manner of a tapered seat to be conical.

A maximally satisfactory contact between one of the two electrodes of the ignition bridge and the inner casing is of considerable importance for the flawless functioning of the electrical primer. In accordance with DOS No. 2,020,016, the provision is made for this purpose to flange the housing against one end face of the inner casing so that the latter, with its other end face, is sufficiently firmly pressed against the electrode. in view of the length tolerances of the individual, seriesdisposed parts, there is, however, the danger under adverse circumstances that, during the flanging operation, the plated element is compressed too greatly in the axial direction and thus is locally overstressed and- /or damaged. In order to avoid this disadvantage, in accordance with another feature of the present invention, the plated element rests, with its face carrying the ignition bridge, against the inner casing, which latter has a bottom with a perforation, this bottom establishing the electrically conductive connection with one of the two electrodes of the ignition bridge.

The perforation is fashioned, in the zone of the ignition bridge, so that the satisfactory ignition of the charge pressed on the ignition bridge is ensured upon the flow of a current through the ignition bridge. The inner casing is inserted by press fit in the housing and, during the pressure introduction of the ignitable charge or charges, is sufficiently firmly pressed with its bottom surface against one electrode of the ignition bridge. Thus, the plated element is advantageously subjected to a uniform pressure load.

In order to still further reduce the electric contact resistance between one electrode of the ignition bridge and the bottom of the inner casing, an electrically conductive annular contact disk can be provided, according to another feature of this invention, between the plated element and the inner casing. The annular contact disk can either be manufactured directly from a very highly electrically conductive material, such as gold, for example, or it can also be merely provided with such a highly conductive surface, for example by gold-plating a bronze ring along its entire surface. In accordance with a further feature of this invention, the electical contact can furthermore be addition-ally improved by forming the annular contact disk, in the not yet installed condition, to be slightly conical, and inserting the disk in the housing so that its inner rim points toward the plated element. In the finished assembled condition of the primer, the contact disk, due to the inherent stress, is then additionally pressed with its inner zone against the plated element and with its outer zone against the inner casing.

Depending on the materials employed for the housing, the inner casing, the contact disk, etc. and the pressure expended when introducing the at least one ignitable charge by means of pressure, a cold welding effect can be advantageously achieved in the zone of the contact surfaces. However, in any event, the inner casing, which preferably is manufactured to be thin-walled of a soft material, such as copper or soft brass, is pressed so firmly against the inner wall of the housing, the contact disk and the plated element, respectively, that the flawless electrical connection is ensured even in case of high shock stresses as they occur, for example, in case of accelerations of 500,000 g.s and thereabove.

In accordance with another feature of the present invention, the inner casing is formed with a wall thickness which decreases toward the end facing away from the plated element. This arrangement has the advantage, for example, that the end of the inner casing facing away from the plated element is sufficiently compressible in the axial direction, and thus tolerances in the axial direction can be compensated for, if this end extends out of the primer housing and serves for supporting the primer on the bottom of the receptacle provided for the primer.

In order to be able to reliably examine by a simple method the pressure application of the at least one primer charge into the inner casing and the pressure contact thereof against the pole piece and/or the plated element, another feature of the present invention provides for the equipping of the at least one ignitable charge accommodated in the inner casing with a cover of preferably metal. The cover caries amarking which is indicative of the flawless conductance of the pressure-feeding step during the pressure feeding of the at least one ignitable charge.

In accordance with the present invention, depending on which composition is conventionally selected for the one charge or also the several series-disposed ignitable charges, the electrical primer of the present invention can advantageously be utilized as a cartridge primer, a detonator, a flame ignition device, or the like.

These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein FIG. 1 is a partial longitudinal sectional view of an electric primer in accordance with the present invention;

FIG. 2 is a longitudinal sectional view of another embodiment of an electrical primer in accordance with the present invention;

FIG. 3 is a plan view of a plated element which may be utilized in accordance with the present invention; and

FIG. 4 is a cross-sectional view of the plated element, taken along line AA of FIG. 3.

Referring now to the drawings wherein like reference numerals are utilized to designate like parts throughout the several views and more particularly to FIG. 1, there is shown a primer including a housing 1 having a pole piece 3 disposed therein and which is electrically insulated from the housing by means of insulation 2 of a synthetic resin, such as polyethylene, for example. The pole piece 3 is accessible from the outside in order to connect the firing circuit, not shown, in the contact bore 4. A plated element 6, which is disc-shaped, shown in an elevational view, is disposed in a recess 5 of the pole piece 3 such that the plated element rests securely with its bottom and peripheral surfaces in the recess of the pole piece 3. An inner casing 7 rests with its bottom 8 having a perforation 9, against one of the electrodes, not shown, of the plated element 6. The bottom 8 of the inner casing 7 is electrically insulated from the pole piece 3 by means of an insulating annular disk 10. The inner casing 7 has its wall in electrical contact with the housing 1, so that the circuit is formed as follows: pole piece 3 first plated element electrode ignition bridge second plated element electrode bottom 8 inner casing 7 housing I.

A first ignitable charge 11, for example a mixture of initiating explosive, reducing agent and oxidizer is inserted by means of pressure into the inner casing 7. The charge 11 is disposed in the zone of the perforation 9 of the bottom 8 of the inner casing, in contact with the ignition bridge, not shown, of the plated element 6, so that it is flawlessly ignited upon current flow through the ignition bridge. The pressure during the pressing introduction of the charge is generally between 1 and about 1,500 kplcm preferably between about 1,000 and 1,500 kplcm The higher the selected pressing pressure, the greater is the attainable shockproofness of the primer element. In the embodiment of FIG. 1, a charge 12 is applied by a second pressing step onto the charge 11; this charge 12 can be a primer charge or also a mixture of explosives. For example, it is possible to employ for the charge 11 a mixture of lead azide, calcium silicide, and potassium perchlorate, and for the charge 12, fashioned as the primer charge, a mixture of calcium silicide, potassium perchlorate, and lead dioxide or if the charge 12 involves a primer mixture a mixture of lead trinitroresorcinate, barium nitrate, and calcium silicide. The purpose for which the electricalprimer is intended, i.e., the type of the powder charge to be ignited thereby, the manner in which it is arranged, etc., determines conventionally which of these and the numerous other possible compositions is selected in each individual case, and whether one or more ignitable charges are utilized.

The inner casing 7 is held in the housing 1 by frictional connection and, in a known manner, additionally by flanging over the upper rim, not shown, of the housing 1 with respect to the corresponding rim of the inner casing 7. The housing 1 and the pole piece 3 consist of a metal, e.g., brass or also a corrosion-resistant steel, such as Cr-Ni steel, for example. The inner casing 7 is manufactured of a softer material, such as copper or soft brass.

in the primer shown in FIG. 2, the plated element 6 rests with its peripheral surface against the wall of the recess 5 of the pole piece 3 by way of the tubular extension 14 of an insulating ring 13. The insulating ring 13 is made, for example, of polyethylene. The extension 14, as well as the wall of recess 5', is of a conical configuration. A contact disk is provided between the bottom 8 of the inner casing 7' and the plated element 6 for aiding in establishing a good electrically conductive path therebetween. The contact disk 15 in the uninstalled condition has a slight conical shape and is inserted in the housing with the inner rim thereof pointing in the direction of the plated element. The two ignitable charges 11 and 12 are covered by a cover or seal 16 of, for example, tin-plated lead foil; during the pressing of the charge or charges and a marking 17 is embossed into this seal 16. The marking 17, here fashioned as a toroid, indicates by its more or less pronounced profile whether the pressing step has been satisfactorily accomplished and thus the functionality of the primer is ensured. In order to provide a watertight assembly, the primer is equipped in the zone of the cover 16 conventionally with a cover layer, not shown, of nitrocellulose lacquer, for example.

The illustrated arrangement of the primer with the end 18 of the inner casing 7 extending out of the housing 1 is specifically intended for use in cartridge ammunition wherein the end 18 takes over the support on the bottom of the chamber provided for the primer and optionally compensates for axial or longitudinal tolerances by compression. As shown in FIG. 2, the inner casing 7' is formed with a wall thickness which decreases toward the end 18 which faces away from the plated element which aids in the compressibility of the casing in the axial or longitudinal direction.

The plated element which may be of the type disclosed in U.S. Pat. No. 3,682,096, as shown in FIGS. 3 and 4 includes a circular-disc-shaped carrier element 21 in the form of an insulating body of, for example, glass or ceramic. The top side is provided with a radially eXtending metallic web of a small thickness and width, forming the glow or incandescent bridge 22, which is enlarged at the outer end thereof into an annular contact surface 23 and whose inner end is extended through a central bore 24 to the circular-disc-shaped contact surface 25 formed on the bottom side of the carrier element 21. The connection between the inwardly disposed end of the heater or incandescent bridge 22 and the lower contact surface 25 can thereby be either self-constructed that the entire cross-section of the bore 241 is filled out, in that part sample, a solid rivet is inserted into the bore 24, or -as indicated in dashed lines in that this connection is limited only to a thin layer along the wall of the bore, which can, for example, be applied simultaneously with other metallic surfaces by galvanic means.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It should therefore be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

We claim:

1. An electrical primer comprising an electrically conductive housing, a pole piece disposed within said housing and accessible from outside of said housing, plated element means disposed within said housing and having an ignition bridge on one surface thereof, an inner casing means disposed within said housing, said plated element means and said inner casing means being arranged in said housing such that said pole piece is electrically conductively connected to said housing via said plated element means and said inner casing means, and at least one ignitable charge being disposed within said housing in operative relation with said ignition bridge for ignition thereby, said pole piece including cup-shaped recess means in the end portion thereof facing said at least one ignitable charge, said plated element means being arranged in said recess means such that at least a bottom surface of said plated element means rests on and is in electrically conductive contact with said pole piece.

2. An electrical primer according to claim 1, wherein said plated element means has a peripheral surface thereof resting against and in contact with said pole piece.

3. An electrical primer according to claim 1, wherein said recess means includes a bottom surface portion and a peripheral wall portion extending therefrom.

4. An electrical primer according to claim 3, wherein said plated element means includes first and second oppositely facing surface portions and a peripheral surface portion therebetween, said ignition bridge being provided on the first surface portion and the bottom surface of said plated element means being the second surface portion thereof.

5. An electrical primer according to claim 4, wherein said plated element means rests with the bottom surface thereof on the bottom portion of said recess means.

6. An electrical primer according to claim 5, wherein said plated element means rests with the peripheral surface portion thereof against the peripheral wall portion of said recess means.

7. An electrical primer according to claim 6, wherein the peripheral wall portion of said recess means is a cylindrical surface portion.

8. An electrical primer according to claim 5, further comprising an insulating member disposed within said housing and contacting said pole piece, said insulating member including a ring portion and a tubular portion extending from said ring portion into said recess means of said pole piece, said plated element means having the peripheral surface portion thereof resting against the tubular portion of said insulating member.

9. An electrical primer according to claim 8, wherein the wall portion of said recess means is conically tapered and the tubular portion of said insulating member has an outer peripheral surface thereof arranged for contact with the wall portion of said recess means and is conically tapered to cooperate therewith.

10. An electrical primer according to claim 9, wherein the wall portion of said recess means diverges inwardly toward the bottom portion of said recess means.

11. An electrical primer according to claim 10, wherein the tubular extension of said insulating member has an inner cylindrical surface portion arranged forcooperatio n with the peripheral surface portion of said plated element means.

12. An electrical primer according to claim 5, wherein said plated element means is arranged for contact with said inner casing means at the first surface portion thereof having said ignition bridge thereon, said ignition bridge including two electrodes, said inner casing means being provided with a bottom surface portion having a perforation extending therethrough, said bottom surface portion of said inner casing means establishing the electrically conductive connection with one of the two electrodes of said ignition bridge.

13. An electrical primer according to claim 12, wherein said inner casing means includes a tubular portion in contact with said housing and adjoining the bottom surface portion thereof, said at least one ignitable charge being disposed within said inner casing means.

14. An electrical primer according to claim 12, further comprising an electrically conductive annular contact disk means disposed within said housing and arranged between said plated element means and said inner casing means for establishing the electrically conductive connection therebetween.

15. An electrical primer according to claim 14, wherein said annular contact disk means is provided with a slight conical shape prior to being disposed in said housing and is disposed in said housing with the inner rim thereof facing in the direction of said plated element means.

16. An electrical primer according to claim 15, wherein said inner casing means includes a tubular wall portion adjoining the bottom portion thereof, said tubular wall portion having a wall thickness which decreases in the direction facing away from said plated W element means.

17. An electrical primer according to claim 5, further comprising sealing means covering the at least one ignitable charge disposed within said housing, and marking means provided on said sealing means for indicating the flawless conducting of the pressing operation for the pressure introduction of the at least one ignitable charge within said housing.

18. An electrical primer according to claim 17, wherein said at least one charge is disposed within said inner casing means arranged within said housing.

19. An electrical primer according to claim 5, wherein a plurality of charges are disposed within said housing.

20. An electrical primer according to claim 16, further comprisng sealing means covering the at least one ignitable charge disposed within said housing, and marking means provided on said sealing means for indicating the flawless conducting of the pressing operation for the pressure introduction of the at least one ignitable charge within said housing. 

1. An electrical primer comprising an electrically conductive housing, a pole piece disposed within said housing and accessible from outside of said housing, plated element means disposed within said housing and having an ignition bridge on one surface thereof, an inner casing means disposed within said housing, said plated element means and said inner casing means being arranged in said housing such that said pole piece is electrically conductively connected to said housing via said plated element means and said inner casing means, and at least one ignitable charge being disposed within said housing in operative relation with said ignition bridge for ignition thereby, said pole piece including cup-shaped recess means in the end portion thereof facing said at least one ignitable charge, said plated element means being arranged in said recess means such that at least a bottom surface of said plated element means rests on and is in electrically conductive contact with said pole piece.
 2. An electrical primer according to claim 1, wherein said plated element means has a peripheral surface thereof resting against and in contact with said pole piece.
 3. An electrical primer according to claim 1, wherein said recess means includes a bottom surface portion and a peripheral wall portion extending therefrom.
 4. An electrical primer according to claim 3, wherein said plated element means includes first and second oppositely facing surface portions and a peripheral surface portion therebetween, said ignition bridge being provided on the first surface portion and the bottom surface of said plated element means being the second surface portion thereof.
 5. An electrical primer according to claim 4, wherein said plated element means rests with the bottom surface thereof on the bottom portion of said recess means.
 6. An electrical primer according to claim 5, wherein said plated element means rests with the peripheral surface portion thereof against the peripheral wall portion of said recess means.
 7. An electrical primer according to claim 6, wherein the peripheral wall portion of said recess means is a cylindrical surface portion.
 8. An electrical primer according to claim 5, further comprising an insulating member disposed within said housing and contacting said pole piece, said insulating member including a ring portion and a tubular portion extending from said ring portion into said recess means of said pole piece, said plated element means having the peripheral surface portion thereof resting against the tubular portion of said insulating member.
 9. An electrical primer according to claim 8, wherein the wall portion of said recess means is conically tapered and the tubular portion of said insulating member has an outer peripheral surface thereof arranged for contact with the wall portion of said recess means and is conically tapered to cooperate therewith.
 10. An electrical primer according to claim 9, wherein the wall portion of said recess means diverges inwardly toward the bottom portion of said recess means.
 11. An electrical primer according to claim 10, wherein the tubular extension of said insulating member has an inner cylindrical surface portion arranged for cooperation with the peripheral surface portion of said plated element means.
 12. An electrical primer according to claim 5, wherein said plated element means is arranged for contact with said inner casing means at the first surface portion thereof having said ignition bridge thereon, said ignition bridge including two electrodes, said inner casing means being provided with a bottom surface portion having a perforation extending therethrough, said bottom surface portion of said inner casing means establishing the electrically conductive connection with one of the two electrodes of said ignition bridge.
 13. An electrical primer according to claim 12, wherein said inner casing means includes a tubular portion in contact with said housing and adjoining the bottom surface portion thereof, said at least one ignitable charge being disposed within said inner casing means.
 14. An electrical primer according to claim 12, further comprising an electrically conductive annular contact disk means disposed within said housing and arranged between said plated eLement means and said inner casing means for establishing the electrically conductive connection therebetween.
 15. An electrical primer according to claim 14, wherein said annular contact disk means is provided with a slight conical shape prior to being disposed in said housing and is disposed in said housing with the inner rim thereof facing in the direction of said plated element means.
 16. An electrical primer according to claim 15, wherein said inner casing means includes a tubular wall portion adjoining the bottom portion thereof, said tubular wall portion having a wall thickness which decreases in the direction facing away from said plated element means.
 17. An electrical primer according to claim 5, further comprising sealing means covering the at least one ignitable charge disposed within said housing, and marking means provided on said sealing means for indicating the flawless conducting of the pressing operation for the pressure introduction of the at least one ignitable charge within said housing.
 18. An electrical primer according to claim 17, wherein said at least one charge is disposed within said inner casing means arranged within said housing.
 19. An electrical primer according to claim 5, wherein a plurality of charges are disposed within said housing.
 20. An electrical primer according to claim 16, further comprisng sealing means covering the at least one ignitable charge disposed within said housing, and marking means provided on said sealing means for indicating the flawless conducting of the pressing operation for the pressure introduction of the at least one ignitable charge within said housing. 